I have a Grubee Skyhawk that just had a cylinder and piston/rings replaced. I've been running 24:1 for nearly 2 gal tanks, keeping it under 20mph for at least 1.5 gals. It was running very well. Started like a top on the first clutch release every time and didn't kill. I started to open it up toward the end of the 2nd gal and I was getting great throttle response and about 30-33mph out of it consistently and was running intermittent WOT for the next 20 miles or so. I had at least 100 miles of taking it relatively easy.
I leaned the mixture out after that to 32:1 and lost some performance and had harder starts. I figured it might be bad carb adjustment. I understand that leaning out a mixture generally allows more gas through, so I initially adjusted the needle down one notch (moved the clip up). I was able to get it started, but it started very hard (only after pedalling a ways with clutch engaged) and had much poorer performance. Now only about 25mph and sluggish. The plug seemed to look rather grey. However, since performance went from bad to worse, I adjusted the needle the other direction, moving the needle up (clip down) to the position just below where I had it for break in. I am now on the bottom clip position on the needle. It will again barely start. Anyone have any suggestions?
FYI: You might also like to know . . . when we were installing the new piston, it was bottoming out on the cyclinder head. The new piston was apparently taller than the old on. We had to install a couple of extra gaskets and shave some aluminum off of the head to get it to fit. After this, it seemed to be running fine till I switched the fuel mixture.
Any help is greatly appreciated!
I leaned the mixture out after that to 32:1 and lost some performance and had harder starts. I figured it might be bad carb adjustment. I understand that leaning out a mixture generally allows more gas through, so I initially adjusted the needle down one notch (moved the clip up). I was able to get it started, but it started very hard (only after pedalling a ways with clutch engaged) and had much poorer performance. Now only about 25mph and sluggish. The plug seemed to look rather grey. However, since performance went from bad to worse, I adjusted the needle the other direction, moving the needle up (clip down) to the position just below where I had it for break in. I am now on the bottom clip position on the needle. It will again barely start. Anyone have any suggestions?
FYI: You might also like to know . . . when we were installing the new piston, it was bottoming out on the cyclinder head. The new piston was apparently taller than the old on. We had to install a couple of extra gaskets and shave some aluminum off of the head to get it to fit. After this, it seemed to be running fine till I switched the fuel mixture.
Any help is greatly appreciated!